Light extracting substrate for organic light emitting diode

ABSTRACT

A light extraction substrate includes a glass substrate having a first surface and a second surface. A first light extraction region can be defined on and/or adjacent the first surface. The first light extraction region includes nanoparticles. A second light extraction region can be defined on at least a part of the second surface. The second light extraction region has a surface roughness of at least 10 nm.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/440,588, filed Feb. 8, 2011, herein incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to organic light emitting diodes, solaror photovoltaic (PV) cells, daylighting windows, and, more particularly,to a substrate having increased light scattering for improved lightutilization.

Technical Considerations

An organic light emitting diode (OLED) is a light-emitting device havingan emissive electroluminescent layer incorporating organic compounds.The organic compounds emit light in response to an electric current.Typically, an emissive layer of organic semiconductor material issituated between two electrodes (an anode and a cathode). When electriccurrent is passed between the anode and the cathode, the organicmaterial emits light, OLEDs are used in numerous applications, such astelevision screens, computer monitors, mobile phones, PDAs, watches,lighting, and various other electronic devices.

OLEDs provide numerous advantages over conventional inorganic devices,such as liquid crystal displays. For example, an OLED functions withoutthe need for a back light. In low ambient light, such as a dark room, anOLED screen can achieve a higher contrast ratio than conventional liquidcrystal displays. OLEDs are also thinner, lighter, and more flexiblethan liquid crystal displays and other lighting devices. OLEDs alsorequire less energy to operate.

However, one disadvantage with OLED devices is that they typically emitless light per unit area than inorganic solid-state based point-lightsources. In a typical OLED lighting device, about 80% of the lightemitted from the organic material is trapped inside the device due tothe optical waveguide effect in which the light emitted from the organicemitting layer is reflected back from the interface of the organicemitting layer/conductive layer (anode), the interface of the conductivelayer (anode)/substrate, and the outer surface of the substrate. Onlyabout 20% of the light emitted from the organic material escapes theoptical waveguide effect and is emitted by the device. Therefore, itwould be advantageous to provide a device and/or method to extract morelight from an OLED device than is possible with conventional methods.

Photovoltaic solar cells are in principle counterparts to light emittingdiodes. Here, the semiconductor device absorbs the energy of light(photons) and converts that energy into electricity. Similar to OLEDs,the efficiency of the photovoltaic device is relatively low. At themodule level, for example, only up to 20% of the incident light istypically converted to electric energy. In one class of photovoltaicdevices, those consisting of thin film PV cells, this efficiency can beas low as 6-7%, depending on the semiconducting material and thejunction design. One way to increase the efficiency of the photovoltaicdevice is to increase the fraction of the solar light that is absorbednear the photovoltaic semiconductor junction. Thus, the presentinvention also finds use in the field of solar cells.

SUMMARY OF THE INVENTION

A light extraction substrate comprises a glass substrate having a firstsurface and a second surface. The light extraction substrate comprises afirst light extraction region and/or a second light extraction region.The first light extraction region, if present, is defined on and/oradjacent the first surface. The first light extraction region cancomprise nanoparticles incorporated into the substrate at a distancefrom the first surface. The second light extraction region, if present,can be defined on at least a portion of the second surface. The secondlight extraction region can have a surface roughness of at least 10 nm.

A light extraction substrate comprises a glass substrate having a firstsurface and a second surface. A first light extraction region is definedon and/or adjacent the first surface. The first light extraction regioncomprises nanoparticles incorporated into the substrate at a distancefrom the first surface. A second light extraction region is defined onat least a portion of the second surface. The second light extractionregion has a surface roughness of at least 10 nm.

A method for making a light extraction substrate, such as a glasssubstrate having a first surface and a second surface, comprises forminga first light extraction region on and/or adjacent the first surface.The first light extraction region is formed by heating the substrate toa temperature sufficient to soften the first surface and then directingor propelling nanoparticles toward the first surface such that at leasta portion of the nanoparticles penetrate the first surface. A secondlight extraction region is formed on at least a portion of the secondsurface. The second light extraction region can be, for example, acoating or a textured pattern. The second light extraction region has asurface roughness of at least 10 nm.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side, sectional view (not to scale) of an OLED deviceincorporating a substrate of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, spatial or directional terms, such as “left”, “right”,“inner”, “outer”, “above”, “below”, and the like, relate to theinvention as it is shown in the drawing FIGURE. However, it is to beunderstood that the invention can assume various alternativeorientations and, accordingly, such terms are not to be considered aslimiting. Further, as used herein, all numbers expressing dimensions,physical characteristics, processing parameters, quantities ofingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, e.g., 1 to 3.3, 4.7 to 7.5,5.5 to 10, and the like. Additionally, all documents, such as but notlimited to, issued patents and patent applications, referred to hereinare to be considered to be “incorporated by reference” in theirentirety. Any reference to amounts, unless otherwise specified, is “byweight percent”.

For purposes of the following discussion, the invention will bediscussed with reference to a conventional OLED device. However, it isto be understood that the invention is not restricted to use with OLEDdevices but could be practiced in other fields, such as, but not limitedto, photovoltaic thin film solar cells. For other uses, such as thinfilm solar cells, the glass architecture described later in thisapplication might have to be modified.

An OLED device 10 incorporating features of the invention is shown inFIG. 1. The OLED device 10 includes a cathode 12, an emissive layer 14,and an anode 18. However, unlike conventional OLED devices, the OLEDdevice 10 includes a substrate 20 incorporating features of theinvention.

The structure and operation of a conventional OLED device will be wellunderstood by one of ordinary skill in the art and, therefore, will notbe described in detail. An exemplary OLED device is described in U.S.Pat. No. 7,663,300. The cathode 12 can be any conventional OLED cathode.Examples of suitable cathodes include metals, such as but not limitedto, barium and calcium. The cathode typically has a low work function.The emissive layer 14 can be a conventional organic electroluminescentlayer as known in the art. Examples of such materials include, but arenot limited to, small molecules such as organometallic chelates (e.g.,Alq₃), fluorescent and phosphorescent dyes, and conjugated dendnmers.Examples of suitable materials include triphenylarnine, perylene,rubrene, and quinacridone. Alternatively, electroluminescent polymericmaterials are also known. Examples of such conductive polymers includepoly(p-phenylene vinylene) and polyfluorene. Phosphorescent materialscould also be used. Examples of such materials include polymers such aspoly(n-vinylcarbazole) in which an organometallic complex, such as aniridium complex, is added as a dopant. The anode 18 can be a conductive,transparent material, such as a metal oxide material, such as, but notlimited to, indium tin oxide (ITO) or aluminum-doped zinc oxide (AZO).The anode typically has a high work function.

Unlike conventional OLED devices, the OLED device 10 is carried on asubstrate 20 incorporating features of the invention. The substrate 20is a transparent substrate having a first surface 24 and a secondsurface 26. Examples of suitable materials for the substrate 20 include,but are not limited to, glass, such as conventional soda-lime silicateglass, for example, float glass. The substrate 20 has a high visiblelight transmission at a reference wavelength of 550 nanometers (nm) anda reference thickness of 3.2 mm. By “high visible light transmission” itis meant visible light transmission at 550 nm of greater than or equalto 85%, such as greater than or equal to 87%, such as greater than orequal to 90%, such as greater than or equal to 91%, such as greater thanor equal to 92%, such as greater than or equal to 93%, such as greaterthan or equal to 95%, at a 3.2 mm reference thickness, Non-limitingexamples of glass that can be used for the practice of the inventioninclude, but are not limited to, Starphire®, Solarphire®, Solarphire®PV, and CLEAR™ glass, all commercially available from PPG Industries,Inc. of Pittsburgh, Pa. The substrate 20 can have any desired thickness,such as in the range of 0.5 mm to 10 mm, such as 1 mm to 10 mm, such as1 mm to 4 mm, such as 2 mm to 3.2 mm.

The substrate 20 incorporates at least one of: (1) a first (e.g., aninternal) light extraction layer or region 30; and/or (2) a second(e.g., an external) light extraction layer or region 32. Adding lightextraction regions in the substrate reduces the waveguide effectdescribed above so that less light is reflected back from the variousinterfaces, and less light is trapped inside the device. This allowsmore light to be emitted from the device. The first extraction region 30is formed by nanoparticles incorporated on the first surface 24 of thesubstrate 20 or embedded in or incorporated into a region of the glassadjacent the first surface 24. Examples of suitable nanoparticlesinclude, but are not limited to, oxide nanoparticles, such as but notlimited to alumina, titania, cerium oxide, zinc oxide, tin oxide,silica, and zirconia. These oxide nanoparticles can be incorporated intothe substrate 20 at a depth in the range of 0 microns to 50 microns,such as 0 microns to 10 microns, such as 0 microns to 5 microns, such as0 microns to 3 microns. The first surface 24 incorporating the firstextraction region 30 can be smoother than the second surface 26. Forexample, the first surface 24 can have an average surface roughness(R_(a)) up to 100 nm, such as up to 50 nm, such as up to 20 nm, such asup to 10 nm, such as up to 5 nm, such as in the range of 1 nm to 100 nm,such as in the range of 1 nm to 50 nm, such as 1 nm to 20 nm, such as 1nm to 10 nm, such as 1 nm to 5 nm.

The external extraction region 32 can be formed by a coating, such as ametal oxide coating having a roughened exterior surface. Examples ofoxides useful for the external extraction layer 32 include, but are notlimited to, silica, alumina, zinc oxide, titania, zirconia, tin oxide,and mixtures thereof. The external extraction layer 32 can have anaverage surface roughness (R_(a)) in the range of 5 nm to 500 nm, suchas 5 nm to 500 nm, such as 50 nm to 500 nm, such as 50 nm to 200 nm,such as 100 nm to 200 nm and/or a root mean square roughness (R_(q)) inthe range of 100 nm to 250 nm, such as 150 nm to 200 nm. The coating canhave a thickness in the range of 10 nm to 500 nm, such as 50 nm to 500nm, such as 100 nm to 500 nm. The external extraction layer 32 can be asingle layer or optionally a multilayer coating.

Alternatively, the external extraction region 32 can be formed bytexturing the second surface 26 of the glass rather than applying aseparate coating layer. For example, the second surface 26 can be scoredor cut to form a textured surface.

The first extraction region 30 and second extraction region 32 canprovide the substrate 20 with haze in the range of 1% to 100%, such as1% to 90%, such as 1% to 80%, such as 1% to 60%, such as 1% to 50%, suchas 10% to 80%, such as 10% to 40%, as measured by a conventionalHaze-Gard Plus hazemeter, commercially available from BYK-Gardner.

Operation of the OLED device 10 will now be described with particularreference to FIG. 1.

During operation, a voltage is applied across the anode 18 and thecathode 12. A current of electrons flows from the cathode 12 to theanode 18 through the emissive layer 14. This electric current causes theemissive layer 14 to emit light. The substrate 20 of the inventionprovides for increased light extraction as compared to an OLED devicewithout the substrate 20. Electromagnetic radiation in the form of lightwaves emitted by the emissive layer 14 travels through the anode 18 intothe substrate 20. These light waves encounter the internal extractionlayer 30 and become more scattered, causing the light waves to travelmore randomly through the substrate 20. When the light waves exit thesubstrate 20 at the second surface 26, the roughened surface of theexternal extraction layer 32 causes further scattering of the lightwaves. The combination of the internal extraction layer 30 scatteringand external extraction layer 32 scattering increases the overall lightextraction for the OLED device 10 by decreasing the wave guide effect.While the above embodiment contemplates the presence of both theinternal extraction layer 30 and the external extraction layer 32, inother embodiments only one or the other of these layers need be present.

An exemplary method of forming a substrate of the invention will now bedescribed.

In a float glass process, glass batch materials are melted in a furnaceto form a glass melt. The glass melt is poured into a float chamberhaving a bath of molten metal, such as a molten tin bath. The moltenglass spreads across the surface of the molten metal to form a glassribbon. In one practice of the invention, a flame spray device orcombustion deposition device is mounted in the float chamber above theglass ribbon. A suitable flame spray device is commercially availablefrom Beneq-Oy Vantaa, Finland. Another flame spray device is describedin WO 01/28941. In the flame spray device, coating materials areatomized, combusted, and then sprayed directly onto the hot float glassribbon. The particles 34 are formed on and/or diffused into the surfaceof the ribbon or penetrate the surface and are incorporated into theupper portion of the float glass ribbon. These particles 34, such asmetal oxide nanoparticles, are present on the surface of the glass orare diffused into the glass and react with the glass matrix. Thisprocess can be practiced at any suitable place in the float chamber butis believed to be more practical at locations where the temperature ofthe float glass ribbon is in the range of 400° C. to 1,000° C., such as500° C. to 900° C., such as 500° C. to 800° C., such as 600° C. to 800°C., such as 700° C. to 800° C. As the float ribbon exits the floatchamber, the glass has nanoparticles 34 embedded in the surface of theglass sheet or incorporated into a region of the glass adjacent theupper surface of the glass. These nanoparticles 34 define the firstextraction region 30. During the incorporation process of nanoparticles34 in the glass surface at an elevated temperature, the glass surfacesmooths out by softening at high temperature. The glass can be heattreated or annealed in a conventional manner.

In a non-float process, the substrate can be heated, such as in afurnace, by a flame, or by another heat source, until the glass surfacehas softened. The nanoparticles can then be directed or propelled at thesoftened surface, such as by a carrier gas. As will be appreciated, thetemperature of the substrate is one factor in determining how far thenanoparticles penetrate into the substrate. As will be appreciated, thelower the viscosity of the substrate, the farther the nanoparticlesshould penetrate. A suitable deposition process is described in U.S.Pat. No. 7,851,016.

After the internal extraction layer 30 has been formed (e.g., after theglass has left the float chamber in a float glass process), the externalextraction layer 32 can be provided. For example, the externalextraction layer 32 can be formed by applying a coating, such as a metaloxide coating, onto the surface of the glass opposite the surface havingthe nanoparticles 34 incorporated therein. This can be accomplished inany conventional manner, such as by conventional sol-gel or spraypyrolysis methods, inside an annealing lehr, or at the exit of theannealing lehr, where the temperature is in the range of 50° C. to 600°C., such as 100° C. to 400° C., such as 150° C. to 350° C., such as 200°C. to 300° C. The resultant substrate thus incorporates both the first(i.e., internal) extraction layer 30 and the second (i.e., external)extraction layer 32. However, in the broad practice of the invention,only one of these extraction regions need be present.

As an additional step (either on-line or off-line), a conductive metaloxide layer to form the anode 18 can be applied in any conventionalmanner over the first surface 24 of the glass substrate 20. For example,a layer of indium tin oxide or aluminum doped zinc oxide can be appliedby magnetron sputter vapor deposition, chemical vapor deposition, or anyother suitable method to form the anode. The anode 18 can be depositedbefore or after the deposition of the first extraction region 30 by anon-line process, or after the deposition of both the first extractionregion 30 and the second extraction layer 32. In addition, an optionalunderlayer coating stack (such as described in U.S. Publication Nos.2010/0285290, 2010/0124642, or 2010/0124643) can be incorporated underthe anode 18 (i.e., between the anode 18 and the substrate 20) toincrease the transmittance of the substrate 20 with the underlayercoating stack and the anode 18 and at least one of the internalextraction region 30 or the external extraction region 32. The substrate20 with the conductive anode 18 and at least one of the internalextraction region 30 or the external extraction region 32 can then besupplied to an OLED manufacturer who can subsequently apply the emissivelayer 14 and the cathode 12 to form an OLED incorporating the lightextraction substrate 20.

Examples of the invention will now be described. However, it is to beunderstood that the invention is not limited to these specific examples.

EXAMPLES

In the following Examples, the substrate (unless indicated to thecontrary) is Solarphire® glass commercially available from PPGIndustries Ohio, Inc. having a thickness of 2 millimeters (mm). The hazeand transmittance values are percentage values and were measured using aHaze-Gard Plus hazemeter commercially available from BYK-Gardner USA.The temperature values are in degrees Fahrenheit (° F.) and the pressurevalues are in pounds per square inch (psi).

Example 1

This Example illustrates a substrate with an external extraction layeron one side. TEOS means tetraethyl orthosilicate; TPT means titaniumisopropoxide; DI water means deionized water; and IPA means isopropylalcohol.

A first solution (as set forth in Table 1) and a second solution (as setforth in Table 2) were prepared. The TPT was added to adjust therefractive index of the coating.

TABLE 1 (SOLUTION 1) MATERIAL AMT. (g) PERCENT (%) TPT 50 24 IPA 50 24HNO₃ 10 5 DI Water 100 48 Total 210 100

TABLE 2 (SOLUTION 2) MATERIAL AMT. (g) PERCENT (%) TEOS 80 21 Ethanol280 72 DI Water 28 7 Total 388 100

These solutions were mixed in the proportions shown in Table 3 and Table4 to form coating composition 1 (Table 3) and coating composition 2(Table 4).

TABLE 3 (COATING 1) MATERIAL AMT. (g) PERCENT (%) Solution 1 10 5Solution 2 190 95 Total 200 100

TABLE 4 (COATING 2) MATERIAL AMT. (g) PERCENT (%) Solution 1 20 10Solution 2 180 90 Total 200 100

The coating compositions were spray applied onto a surface of ovenheated glass substrates using a conventional spray coating device toform an external extraction layer. As set forth in Table 5, theresultant coatings provided the substrate with haze greater than 10while still maintaining transmittance greater than 90 percent.

TABLE 5 COATING SPRAY OVEN TEMP AIR PRESSURE HAZE TRANSMITTANCE SAMPLE #COMPOSITION TIME (min.) ° F. (psi) (Post-Spray) (Post-Spray) 1 1 5 45050 11.8 94.4 2 1 10 450 50 21.1 94.2 3 2 5 450 50 10.3 94.1 4 2 10 45050 23.1 94.0

Example 2

This Example illustrates a coated substrate with an external extractionlayer on one surface and an indium tin oxide coating on an oppositesurface. A coating of indium tin oxide (ITO) was sputter deposited ontoa first major surface of a glass substrate from an indium/tin cathodeusing a conventional magnetic sputter vapor deposition (MSVD) device.The ITO coating had a thickness of 300 nm. An external extraction layerwas applied by conventional spray pyrolysis onto the second majorsurface of the glass substrate (opposite the first major surface) usingthe coating compositions described above. The spray parameters andoptical results are shown in Table 6.

TABLE 6 SPRAY AIR HAZE HAZE COATING TIME OVEN PRESSURE (Pre-TRANSMITTANCE (Post- TRANSMITTANCE SAMPLE # COMPOSITION (min.) TEMP ° F.(psi) Spray) (Pre-Spray) Spray) (Post-Spray) 5 1 5 450 50 0.14 86.9 11.887.2 6 2 10 450 50 0.12 87.5 19.7 87.6

Example 3

(A) This Example illustrates a substrate with a slime based externalextraction layer. Hi-Gard® HC 1080 coating composition (commerciallyavailable from PPG Industries Ohio, Inc.) was spray applied onto asurface of oven heated glass substrates using a conventional spraycoating device to form an external extraction layer. The sprayparameters and optical measurements are disclosed in Table 7. The coatedsubstrate had haze greater than 50 percent while still maintainingtransmittance greater than 87 percent.

TABLE 7 Factors Spray Sample Time Air Oven Post Spray number (sec.)Pressure (psi) Temp ° F. Haze Transmittance 7 5 40 500 66 92 8 10 40 50071.2 90.1 9 5 40 500 64.9 87 10 5 40 550 59.7 92.3 11 7 40 550 70.6 91.612 5 40 600 71.4 88.1 13 5 75 550 64 92 14 5 60 550 69 91.8 15 5 75 50071.7 91.7 16 5 75 450 72.8 91.7 17 5 60 450 74.5 91.6 18 5 40 450 63.892.2

(B) A Hi-Gard® HC 1080 coating was spray applied to one side of a glasssubstrate as described above. An indium tin oxide coating of 300 nm wassputter deposited on the opposite side of the substrate using aconventional MSVD coater. The spray deposition parameters and measuredoptical data are set forth in Table 8. The coated substrate had hazegreater than 50 percent while still maintaining transmittance greaterthan 81 percent.

TABLE 8 Factors Spray Pre-spray Post-spray Sample Time Air Oven ReadingsReadings number (sec.) Pressure (psi) Temp ° F. Haze Transmittance HazeTransmittance 19 5 40 400 0.09 86.1 57.5 84.6 20 10 40 400 0.12 85.968.7 84.1 21 10 40 400 0.13 85.2 76.8 83.1 22 5 40 400 0.12 87.5 66.285.6 23 4 40 400 0.13 87.5 56.2 86.1 24 10 50 400 0.11 84.3 65.8 82.9 253 40 400 0.14 84.2 56 82.8 26 5.5 75 400 0.12 83.6 77.7 81.2 27 5.5 75400 0.11 85.7 74.5 83.4

Example 4

This example illustrates a substrate having an internal extraction layer(region). The internal extraction layer was formed using a conventionalflame spray device, such as an nHalo flame spray coating devicecommercially available from Beneq Oy. The coating compositions wereselected to form either alumina or titania nanoparticles. Samples 28 to31 below contain alumina nanoparticles. Samples 32 to 39 contain titaniananoparticles. The nanoparticles were present at a depth in the range of0 nm to 10 nm from the surface of the glass. As a general rule, as theconcentration of nanoparticles increases, the haze increases and thetransmittance decreases. Haze and transmittance values were measured onthese samples as listed in Table 9.

TABLE 9 Sample number Haze Transmittance 28 5.22 93.0 29 14.9 91.7 3030.2 89.5 31 35.8 89.9 32 82.7 69.4 33 63.3 69.9 34 44.0 78.0 35 68.671.0 36 55.5 74.6 37 73.6 74.1 38 78.0 69.5 39 62.9 74.1

Example 5

This Example relates to a coated substrate having both an internalextraction layer and an external extraction layer. An internalextraction region was formed by softening the first surface by heatingand then directing titania nanoparticles at the first surface such thatat least a portion of the nanoparticles penetrated below the firstsurface. This was done using a flame spray device such as describedabove. The resultant substrate with the internal extraction layer had ahaze value (percent) of 55.6 and a transmittance of 74.4 percent. Anexternal extraction layer was formed on the second surface of thesubstrate by heating the substrate in an oven for eight minutes at 450°F. and then spray applying a Hi-Gard® HC 1080 coating composition(commercially available from PPG Industries Ohio, Inc.) onto the secondsurface using a conventional spray coating device as described above (40psi for 10 seconds) to form the external extraction layer on the secondsurface. The substrate with both the internal extraction layer and theexternal extraction layer had a haze of 94.4 percent and a transmittanceof 74.6 percent.

It will be readily appreciated by one of ordinary skill in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

What is claimed is:
 1. A light extraction substrate, comprising: ahomogenous glass substrate having a first surface and a second surfaceopposite the first surface; a first light extraction region adjacent thefirst surface, the first light extraction region comprisingnanoparticles embedded in the homogenous glass substrate at a depth of 0to 50 microns, and wherein the first surface has an average surfaceroughness of up to 10 nm; and a second light extraction region on atleast a portion of the second surface, wherein the first lightextraction region and the second light extraction region provide haze inthe range of 10% to 40%; and wherein the second extraction region has anaverage surface roughness in the range of 50 nanometers to 500nanometers.
 2. The substrate of claim 1, wherein the nanoparticles areselected from the group consisting of silver oxide, alumina, titania,cerium oxide, zinc oxide, tin oxide, silica, zirconia, and combinationsthereof.
 3. The substrate of claim 1, wherein the second extractionregion comprises a coating.
 4. The substrate of claim 3, wherein thecoating is selected from the group consisting of silica, alumina, zincoxide, titania, zirconia, tin oxide, silicate coatings, and mixturesthereof.
 5. The substrate of claim 1, wherein the second extractionregion is formed by texturing the second surface.
 6. The substrate ofclaim 1, further comprising an anode layer deposited on the firstsurface.
 7. The substrate of claim 6, wherein the anode comprises indiumtin oxide or aluminum doped zinc oxide.
 8. The substrate of claim 1,wherein an underlayer coating stack is deposited on the first surfaceand an anode layer is deposited on the underlayer coating stack, theunderlayer coating stack boosts transmittance of the glass substratewith the anode layer and with the first or second extraction region. 9.The substrate of claim 1, wherein the first surface is smoother than thesecond surface.
 10. The substrate of claim 1, wherein the depth is 0microns to 10 microns.
 11. The substrate of claim 1, wherein thehomogenous glass substrate consists of conventional soda-lime silicateglass.
 12. The substrate of claim 11, wherein the conventional soda-limesilicate glass is float glass.
 13. A light extraction substrate,comprising: a homogenous glass substrate having a first surface and asecond surface opposite the first surface; a first light extractionregion comprising nanoparticles embedded in a region of the homogenousglass substrate adjacent the first surface at a depth of 0 to 50microns, wherein the first surface has an average surface roughness ofup to 10 nm; and a second light extraction region on at least a portionof the second surface, the second light extraction region having anaverage surface roughness in the range of 50 nanometers to 500nanometers.
 14. The substrate of claim 13, wherein the nanoparticles areselected from the group consisting of silver oxide, alumina, titania,cerium oxide, zinc oxide, tin oxide, silica, zirconia, and combinationsthereof.
 15. The substrate of claim 13, wherein the light extractionsubstrate has haze in the range of 10% to 90%.
 16. The substrate ofclaim 13, further comprising an anode layer deposited on the firstsurface.
 17. The substrate of claim 13, wherein an underlayer coatingstack is deposited on the first surface and an anode layer is depositedon the underlayer coating stack, the underlayer coating stack booststransmittance of the glass substrate with the anode layer and with thefirst or second extraction region.
 18. The substrate of claim 13,wherein the first surface is smoother than the second surface.
 19. Thesubstrate of claim 13, wherein the depth is 0 microns to 10 microns. 20.The substrate of claim 13, wherein the homogenous glass substrateconsists of conventional soda-lime silicate glass.
 21. The substrate ofclaim 20, wherein the conventional soda-lime silicate glass is floatglass.
 22. A light extraction substrate, comprising: a homogenous glasssubstrate having a first surface and a second surface opposite the firstsurface; and a first light extraction region adjacent the first surface,the first light extraction region comprising nanoparticles embedded inthe homogenous glass substrate at a depth of 0 to 50 microns, andwherein the first surface has an average surface roughness of up to 10nm; wherein the first light extraction region provides haze in the rangeof 10% to 40%; wherein the homogenous glass substrate consists ofconventional soda-lime silicate glass; and wherein the conventionalsoda-lime silicate glass is float glass.